Apparatus for polishing metals



June 14, 1960 w. HELLING ET AL 2,940,228

APPARATUS FOR POLISHING METALS Original Filed July 3, 1956 n r Helling Bra-H h Numzig WMJM HTTORNEJ United States Patent APPARATUS FOR POLISHING METALS Original application July 3, 1956, Ser. No. 595,792. Di-

vided and this application Aug. 22, 1957, Ser. No. 679,685

Claims priority, application Germany July 8, 1955 7 Claims. (Cl. 51-263) The present invention relates to an apparatus for polishing metals and, more specifically, it relates to an apparatus for forming a highly glossy surface on metal bodies.

The present application is a division of our copending application Serial No. 595,792, filed on July 3, 1956 and entitled Method and Apparatus for Polishing Metals.

Customarily wet-polishing operations are carried out with polishing apparatus having polishing wheels, the working surfaces of which are covered with cloth or felt, or with polishing wheels which in their entirety consistof cloth or felt (so-called flexible bulfing wheels). Further! more, textile bands are also used for this purpose. By employing any of the aforementioned polishing members it is not possible to achieve an especially high gloss, to the contrary there always remains microscropically fine scratches, which for instance give to such polished metal surface an undesirable cloudy luster. It is a further disadvantage of the above-discussed devices that the textile materials absorb and retain only small quantities of the polishing fluid. Consequently, textile covered polishing wheels cause spinning off of considerable quantities of the polishing fluid due to the centrifugal forces created by the rotating polishing wheel. The spun-off polishing fluid circulates Without useful eflect.

it is therefore an object of the present invention to overcome the aforementioned disadvantages of conventional wet-polishing apparatus.

It is another object of the present invention to provide a Wet-polishing apparatus including a polishing member capable of absorbing and retaining relatively large quantities of polishing fluid.

It is a further object of the present invention to provide a wet-polishing apparatus including a rotating polishing member which may be rotated at a very low surface speed while still effectively polishing metal surfaces.

It is still another object of the present invention to provide a wet-polishing apparatus, during operation of which the losses on polishing fluid are reduced to a minimum.

it is yet another object of the present invention to provide in a wet-polishing apparatus a polishing member capable of imparting a very high gloss to metal surfaces.

Other objects and advantages of the present invention will become apparent from a further reading of the description and of the appended claims.

With the above and other objects in view, the present invention mainly comprises in a polishing apparatus adapted to wet-polish the surface of a metal body, a polishing member having a working outer portion consisting of a porous plastic material.

It should be noted that throughout the present application and claims the term porous is meant to indicate open pores or a mixture of open and closed pores, but does not include exclusively closed pores.- The term porous is further meant to indicate that the structure of the porous material is such that a liquid can pass through interconnected open pores throughout the entire body of the material.

' According to a preferred embodiment of the present 2 invention, the same includes-a polishing apparatus 'for wet-polishing the surface of a metal body, comprising, in combination, a rotatable polishing disc consisting essen: tially of a porous plastic material belonging to the group consisting of natural and synthetic rubbers, viscose, urea resins, phenolic resins, polyurethanes, polystyrenes and polyvinyl chlorides, the size of the pores in the porous plastic material being between about and 1,000 microns, rotating means for rotating the polishing disc and including a rotatable shaft having a hollow perforated portion, the porous disc being mounted on the hollow perforated shaft portion, collecting means for collecting polishing fluid separating from the polishing disc during operation of the polishing apparatus, and pumping means communicating with the collecting means and with the hollow perforated shaft portion for passing polishing fluid from the collecting means into the hollow perforated shaft portion, whereby upon rotating of the shaft polishing fluid will pass through the perforations of the hollow shaft portion into the porous polishing wheel and to the outer Working surface thereof due to the centrifugal force exerted by the rotating porous polishing ,wheel.

Surprisingly, it has been found according to the present invention that a considerable increase in the quality of the polish and gloss of aluminum and aluminum alloy surfaces as Well as of other metal and metal alloy surfaces can be obtained by employing instead of textile. polishing Wheels, polishing wheels or bands which have at least a working surface made of porous plastic'materials. Elastomers such as natural or synthetic rubber, viscose, urea or phenolic resins, polyurethanes, polystyrenes, polyvinyl chlorides and others may be employed. The polishing wheels or bands or other polishing members may be formed completely of such porous plastic materials or may be entirely or in part covered with the same. Preferably, materials having open pores of a size between 100 and 1,000 microns are used.

A further advantage of employing such porous elastomers consists in the reduction of the required speed of the wheels or hands as compared with the speed requiredwhen using the customary felt or cloth polishing members. Consequently, the centrifugal forces are less, the polishing liquid is absorbed into the pores of the polishing member and retained therein without being spun off in large quantities due to excessive centrifugal forces.

The discs or wheels made of such synthetic or natural elastomers, or at least having working surfaces covered with the same, absorb the polishing fluid and retain a large portion of the same, since the centrifugal forces, due to the slow surface speed do not cause any spinningoif of polishing fluid. It is a further advantage of the polishing members according to the present invention that the metal or metal alloy body which is to be polished can be strongly pressed onto the working surface of the disk which can be formed of commensurate Width. Thereby the metal body will partially be embedded into the surface of the plastic porous disk under temporary deformation of the disk. In this manner it is possible also to polish metal bodies which have an uneven surface such as reliefs or portions of mountings, instruments and the like, since the polishing disc acts on a larger portion of the surface of the metal body. Thereby too, the pol-.

ishing fluid is for all practical purposes retained in the porous plastic wheel and is not spun-ofl.

The surface speed or rim speed of polishing wheels or bands made of porous elastomers can be as low'as between 2 and 3 meters per second. At such low speed. many of the dangers which otherwise exist when polishing uneven bodies are avoided. Customary polishing discs having textile covered Working surfaces or polishing bands of customary textile material have to be operated at considerably higher'speeds such as speeds of between Patented June 14, 1960 ves 20 and 3O meters per second since otherwise the polishing al bodies of vcizlmplicateduneven configuration. Acingly.thepreviouslyexisting diificulties jin the wettag of metal bodies with. suspensions of solid par: $111 a' liquid medium .can be avoided by'employing the polishing members of the present invention which have least working surfaces made of porous natural or, synthetieelastomersr .Thernovel'features which are. considered as charac;

teristic for theiinvention are set forthiin particular in The invention itself, however, both the appended claims. I as its. construction ,anditsmethod :of operation, to

g? ei..with Iadditional objects and.advantages thereof, willbebest understood from thefollowing .descriptioniof eifec't can ons shamed; The danger, as'iswell knownf consists in the possibility thfli'. t e metal body may attach itself to the fast moving polishingmember and may then; b "thrown loff, the same, 7 Consequently; the low speed s plastic polishing wheels ,or bands according to-the en'tginvention are especially. suitable for. polishing,

S11 embodiments, whenflread in connection withthe 7 .9 b y aw ngs-g n WhiQhI "Fig.1 i sla'sche matic elevationalview of an embodiment,

, of the appar atus ofthe present invention; 7

Fig. 2 is a -schematic..elevationalview .of' another embodiment [of an. apparatus according to the present inventionand Fig. 3 is-still anotherschematic elevational view 'diifer'ent embodiment of the present invention.

Referring .now to th drawing and particularly to Fig; 1, a motor l1 isfshown driving a shaft 2. On shaft 7 V 2 i ,inounted a polishing wheel orrdisc 3 having an outer f wqrlsing portion 4, the working surface ofwhich will corr eingc onta ct with the metal body to be polishedi worlging portions' 4 ofpolishingmemberS is madeof; aporous. plastic, material adapted to apply a polishing fluicl tiothe metalbody, Polishing fluidrsqueezed out of theporous plastiqworking portion of polishing member 3 iscollected in a-vessel 5 and pumped v by pump 6 through conduit 7, from the open end ofwhich the polishing fluid. is again introduced to the porous plastic working. P rtion 4 .bfi lpolishing. member 3. The polishing ,fluid, while thegmetal, body is collected and returnedto thepolishing; wheel :as indicated in tthesdescrip ou; otth 1 raw n of a a passing, through conduit 7 is .coo1ed:by cooling means, 8.;

Mhtor" land .shaftIZ constitute. the rotating means, COD-.2

: duit 7 is an embodiment of the liquid-introducing means collecting means are represented byvessel 5,*-an d pump 6" together with the conduit connecting vessel 5 with pump,

6 'representl the pumping means;

The diiferent embodiment shown n Fig. 2 includes a Qshaft portion 11 as part of ,the rotating means, 3 on is rnounted .a polishing whe'el 12, whichis made of aporous plastic material, .Braekets, 13wv are {led-for givingadditional support to polishing mem-. 6F; slz k q ish n u s pump through com duit 14;;jnto. hollow shaft 11 and enters the porous plasticpolishing wheel 12 ;through hollow perforated .portioni 'll," Polishing fluid squeezed off the work- .ingsurface of polishingiwheel 12 when the same is in A" somatic of finely poro V polyurethane, having a pf about l00 mm. and aidiameter "of about 30 0 The porousmlastic; materials otwhi hth ntire :PQH.

wheel is mounted on a shaft by means of two lateral brackets preferably made of wood, hard rubber or a suitable strong synthetic material and having rounded edges. The polishing wheel is rotated with about 160 turns per minute corresponding, to a peripheral velocity of about 2. 5 .mete'rs'persecond. The .wheel islcompletely saturated with polishing fluid consisting for instance of a peus an f. lu num ydrat g z lu na. in.-

water. to. whicha smalljquantity of .a commercial wetting agentlhasbeenndgledn, Thelmetalrbcdies to 'be,.polished are firmly pressed against the polishingwheel sothat they penetrate tosome extent into theVresil-ient Working surface thereof; Thereby polishing fluid is pressed out of the polishing wheel and due to the low velocity this fiuid rernains for a short periodof time on the surface of the metal body= from-which'-the-fluid: slowly-drops into a collecting vesseL; It should be. notedthat due to the low velocity and correspondingly small centrifugal force, sPOl S -fl1 ici not. :spuue ftrme pol shi g. wh .cl- Consequentlh i zi inottneecssa o p ovidebaflie. sheets oriother protectivesdeyicesitocatqhpolishing lfl id spr y-.. ing .ofi-sthe. appar tus -,.;.,The P l hing;' l QLdIYOPP'lI g fI'Om i hi s wheehmaybe rmed re...a1so w ll suit for condu ting thepolishingfluid :to the workingsurface ofthhpqlishing wh elnfor ins ance y Providi g-.21 hol ow s ftomwhi h, the, polishing. Wheel -;is;.mQunted-;and. through which the poli hing. fl id .is supplied; This has .bcenillu ed in. Fig.1.," 'I'herpolishingfluid may. also be. pressed into the, m llinterv n gspace-betweens wmel p l hins els. which arle mounted next; to each; other; In; this manner,; too, vthe,poli hingsfluid can be supplied to .the working,

surface of t p ishin W e J;

The. ifi renceinagloss;obtainedon metal surfa es of: the, same, compositionv and -under otherwise equal condi-,

tions byreplaci g heconventionaltextile polishing mem:

oer of, a. weirpqlishing; apparatus with, the porous, plastic polishinglmemben according; ;to, .theprescnt, invention isillustrate inif blel f rther below:

The examples which are; summarlzecl,iu 'Iab1ev I aresir n. illustrativ gonlyr the present invention; however,

not :beingjimitedto, anysof; the, specific: details, of: the,

examples. 7

An aluminum magnesium alloy body including 0.01%' Cu, 0.011% Zn, 0.066%*Si*,"0.03 3.%*Fla 0.002%" Mn, 1.92% Mg and the balance aluminum, in the formof a normalcommercial sheet withea cold rolled finished surface, I was first dry-polished Wll'.h;a polishing paste ,consisting of 66'parts offinely sub-divided alumina, 26 parts of stearin, 6 parts of montan wax,;and 2 partsiof petroleum jellyj. The dry polishing 'was carried 'out with a flexible polishing wheel made, of nettle cloth, having a diameter of 300mm. and a width of 40mm. The dry polishing was, carried outat a circumferential speed of 50 metersl-per second for a period of, 2 minutes The drypolished metal body'was then pickled by immersion for 30secondsina 10% aqueous sodium hydroxide solution having a temperature of 55 'C.', subsequent rinsing with water followed by neutralization by immersion for a short periodiof time in 20% :aqueous nitric acid at m t sret e e u eng ge-m ta 'q yrw t uw q d with a'conventional textile polishing whe'el. "A polishing fluid prepared by, diluting 300 cubic centimeters of a commercial suspension of' polishing alumina (Number 3 V of the firm Jean, Wirtz, Dusseldorf) withl liter of water mounted'on a grinding head in a manner similar I to themounting of a grinding wheel. The pores of the polyurethane wheel; preferably ilhave a size ofbetween 100 and, 1,000 microns. 'I'he polyurethanq polishing;

ia idiii ref 3 r ms an. s e y l: cellulose-ofviscosityXTylose SI; 400ma'de by Kalle o ba s ieb i i w s-r The flexible polishing wheel consisted ,of several layers of absorbent soft 'cotton' which had 'been sewn together. hefi aa t $hqpql biaaw lnas 0 me d t width 40 The circumferential speed of the rotating polishing wheel was 20 meters per second. The abovedescribed polishing fluid was sprayed onto the polishing wheel. Wet polishing was carried out for a period of minutes. Thereafter, the metal body was sprayed with water.

Finally, the metal body was anodically oxydized for 10 minutes in aqueous sulfuric acid at 18 C. with a current density of 1.5 amperes per 100 square centimeters. The thus obtained oxide layer had a thickness of approximately 5 microns.

A parallel experiment was carried out exactly as described above, with the only exception that the wetpolishing was accomplished with a porous plastic polishing wheel in the following manner:

The same wet-polishing liquid was used as described above. The polishing wheel was made of finely porous polyurethane (Moltopren 0.055 blue, thickness 10 centimeters made by Pongs & Co., Aachen). The wheel had a diameter of 300 mm. and a width of 100 mm. and was mounted on a grinding head in a similar manner as a grinding wheel. The wheel was rotated with 160 revolutions per minute, corresponding to a circumferential speed of about 2.5 meters per second. The wheel was completely saturated with polishing fluid, the polishing fluid which dropped oif the wheel and/or the metal body was caught and recirculated to the polishing wheel. Polishing was carried out for 4 minutes.

EXAMPLE 2 Parallel experiments were carried out as described in Example 1, however, the sheets which were thus-treated were made of an aluminum magnesium alloy containing 99% of high purity aluminum (99.99% aluminum) and 1% magnesium.

EXAMPLE 3 Commercial cold rolled brass sheets were first drypolished and thereafter wet-polished either wiith a conventional cloth polishing wheel or with a porous plastic polishing Wheel, as described above.

In all of the above-described experiments, the total and specular reflection of the finished product was measured and the following values were found:

It is apparent from the results shown in Table 1 that considerably higher reflection values are obtained with the polishing apparatus according to the present invention as can be obtained under otherwise equal conditions with conventional polishing apparatus.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of polishing apparatus differing from the types described above.

While the invention has been illustrated and described as embodied in a polishing apparatus, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential charac- 6 teristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and "are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a polishing apparatus for Wet polishing metal bodies so as to obtain a glossy surface thereon, in combination, a polishing member having a continuous outer working portion consisting essentially of an open-cell, porous, elastomeric plastic material; feeding means for feeding a polishing suspension onto said outer working portion of said polishing member at a portion thereof spaced from the area of simultaneous contact between a metal body to be polished and said polishing member, to be absorbed by the same and to be squeezed out of the same at a polishing surface thereof when the article to be polished is pressed against said polishing surface; collecting means for collecting polishing fluid squeezed out of said polishing member and for returning collected polishing fluid to said feeding means; and automatic means for rotating said outer working portion of said polishing member at a circumferential speed sufiiciently low to substantially prevent the spinning off of polishing suspension due to centrifugal force, relative to and in contact with the surface of a metal body to be polished.

2. In a polishing apparatus for wet polishing metal bodies so as to obtain a glossy surface thereon, in combination, a rotating polishing member having a continuous outer working portion consisting essentially of an opencell, porous, elastomeric plastic material; feeding means for feeding a polishing suspension onto said outer working portion of said polishing member at a portion thereof spaced from the area of simultaneous contact between a metal body to be polished and said polishing member, to be absorbed by the same and to be squeezed out of the same at a polishing surface thereof when the article to be polished is pressed against said polishing surface; collecting means for collecting polishing fluid squeezed out of said polishing member and for returning collected polishing fluid to said feeding means; cooling means between communicating with said collecting means and said feeding means for cooling polishing suspension flowing from said collecting means to said feeding means and automatic means for rotating said outer working portion of said polishing member at a circumferential speed sufficiently low to substantially prevent the spinning off of polishing suspension due to centrifugal force, relative to and in contact with the surface of a metal body to be polished.

3. In a polishing apparatus for wet polishing metal bodies so as to obtain a glossy surface thereon, in combination, a polishing member having a continuous outer working portion consisting essentially of an open-cell, porous, elastomeric plastic material; feeding means for feeding a polishing suspension onto said outer Working portion of said polishing member at a portion thereof spaced from the area of simultaneous contact between a body to be polished and said polishing member, to be absorbed by the same and to be squeezed out of the same at a polishing surface thereof when the article to be polished is pressed against said polishing surface; and automatic means for moving said outer working portion of said polishing member and the surface of a metal body to be polished.

4. In a polishing apparatus for wet polishing metal bodies so as to obtain a glossy surface thereon, in combination, a polishing member having a continuous outer working portion consisting essentially of an open-cell,

porous, elastomeric plastic material selected from the group consisting of natural and synthetic rubbers, vis- 7'- ishing suspension onto said'outen v vork-ing portionoi said" polishing memb'er -at a portion thereof spaced fromthe afea of similltaneous contact between a metal body--to be polished and said-polishing memben, to-beabsorbedby-tlie same-and to be-squeezed but of 'the sameata polishing surface thereof when the article -to be-polished is' pressed against said polishing surface; collecting means for-collectingpolishing fluid squeezed out of said polishing-membeP-andfor-Jretuming collected-polishing fluid tosaidfeeding -mejans; andautornatic means fonmovement bet-weenqetating said-outer Working portion of said polishing ;m ernber--at a cirenmferentialespeed sufficiently loweto substantmly-prevent-the spinning off 'of-polishingt SDSFBSiOiI- d1l-jf0 cent-rifugal force, relative '-to and in contaet-Wit-lr'the surface of a niet-al body to be--Polished.'- 5; polishing apparatus -for- .wet polishing metal bodies-so-esto obtain a glossy-surfaeeethereon, in combin'ation a polishing disoconsisting essentially of an open-- eel-l porous; elastome r ic; plastic material-"and having acon't-inuous'eoutep working-portion; feeding means for feedingx a polishin'g suspensiomonto said outer Working portion=of jsaid= polishin'g 'disk -at -a --portio'n thereof spaced from the-area ofi simultaneous contact between a metal; body -to be polished and.-said polishing-member, to be absorbed -by; the "-same--'and- 'to'-b'esqueezed out of the same -at-jmpolis'hing'surface thereof when the article to be-polished is pressed against, said'polishing surface; collecting-- means ion-collecting polishing -fiuid squeezedout o'f said-polishingmember and for returning collected polishing fiuid to' said feedingmeans; and automatic means forrotating said polishing disc at a circumferentialspeed' of up-toaboutfi meters per second relative to ancl in contactwithth'esurface ofa metal body to be polished.

6iln a=polishihg--apparatus-fop wetpolishing metal' bodies so as to -obtain -a glossy surface thereon, in combinationg a polishing belt consisting essentially of an open-cell, p0rous, elastomerie plastic material and having a lieontinuous outel working portion; 7 feeding means for feedingi-a polishing-suspensiononto said outer Working portion ofisaid polishing-belt ata portionthereof spaced from=the;. area-ofsimultaneous contact between'a metal body tobe polished--and said polishing member,"to be absorbed by the samesandetonbeasqueezedeouteofsiher san e at a polishing suxfaeea theneof when lh ewalicide mn' be polished 'i's' p e's'sed against' saidJpolishing sutface; col-1'1.

leetingmeans -for colleeting pelishing flnid isqueezedsoutofsaid iaolishing'memben and for returningmollectedipol ishing fluid to said feeding means; and automatic means for -moving said polis'hin g belt at 'a speed oi up to -about 3 meters per second relative towand-"in contact with%the surfa'ee of a metal-body to bepolished; 7 a: In a polishing-apparatus for: wet polishing -metalbodies so as to obtain a glossy surface- -thereon;in -com binatiomt a rot-ating polishing membenconsistingessentially' ofamopemcell; porous; elastomeric plastic materiab selected fromathe group consisting of naturaland synthetic rubbers, viscose; nrearesins; phenolic resins polyureth'anes; polystyrenes and: polyvinyl; chlorides --=-and formed With-interconnected openedapores-having diame- (81'8-0f between-about =100 and l0o0iinicronsg'means for; feeding a polishing suspension--to-=said polishing--member at-aportiomthereof spaced ifom-the-area-i of simultaneous contact -between--a -metal body toibe polished -and said polishirigmembento-be:absorbed by--th'e same and-to-be$ squeezed out -of= tlie -sa'me atapolishing surface thereof when the articleto be polished-is; pgessed against-said polishing surfaca-jand means" for rotating said polishing- 1 niernber' at a circumferential speed-0f betWeen Q and meters 'per- -second grelative" =to and- 'in contact withathe' surface of a metal body to-b'e polishedlr 4 References Citd in the file of this patent ,ITIEDT ATES P T /I V 

